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Figure 3. Concrete Mapping
To relate the EmployeePart table to the PersonPart table requires that they share a common value—in this case, the name column. The PartTimePart, FullTimePart, and ManagerPart tables are necessary to perform a full vertical mapping of the concrete classes in this model. Without them we cannot tell whether objects should be instances of PartTime, FullTime, Exempt, or Manager. |